Subsea systems such as well trees for subsea hydrocarbon extraction or injection wells, subsea manifolds and subsea distribution units are supplied with at least one of (for example) electric power, hydraulic power, control signals and chemicals via an umbilical, from a surface platform or surface vessel for example. The umbilical is terminated at the sea bed by an umbilical termination assembly (UTA). Typically, the UTA is mounted on a frame which in turn is attached to a foundation, normally a mudmat. Standard practice is to lower the mudmat to the sea bed first, whereupon it is installed at the required location so that the skirt of the mudmat penetrates the surface to provide lateral movement resistance and the top of the mudmat is level with the sea bed surface.
FIGS. 1a and 1b show, diagrammatically a method of installation of a UTA. In FIG. 1a, a frame 1 has been lowered to the sea bed attached to a mudmat 2. The next step is to lower the UTA 3, attached to an umbilical 4, and locate it on the frame 1. This is effected by a remotely operated vehicle (ROV), by aligning a pin (i.e. stab 5) with a funnel 6 connected to the frame. As shown in FIG. 1b, the UTA 3 is typically hinged at the top of stab 5, so that after location on the frame 1, continual laying of the umbilical 4 allows it to rotate from the vertical position to the horizontal as the umbilical 4 is laid on the sea bed. To complete the installation, appropriate links are then connected from a connector 8 on the UTA 3 to a subsea system (not shown) such as a well tree.
The above sequence of operations involves substantial use of an ROV, which is an expensive process. Furthermore, the mounting of the UTA on a foundation framework results in it being, typically, some six feet above the sea bed, resulting in the need for several bend restrictors 9 attached to the umbilical 4 between the UTA 3 and the point where the umbilical meets the sea bed.